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Classification of Life

Classification of Life. Why Classify Organisms?. To aid them in their study of the large diversity of organisms, biologists classify organisms by naming them and by grouping them in a logical manner. Taxonomy is the discipline scientists use to classify and name organisms.

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Classification of Life

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  1. Classification of Life

  2. Why Classify Organisms? • To aid them in their study of the large diversity of organisms, biologists classify organisms by naming them and by grouping them in a logical manner. • Taxonomy is the discipline scientists use to classify and name organisms.

  3. Binomial Nomenclature • From the time of Aristotle until the 1700s, all living things were classified into two kingdoms, the plant and animal kingdom.

  4. In the 1700s, Carolus Linnaeus, a Swedish botanist, developed a classification system based on Carolus Linnaeus 1707 - 1778

  5. anatomical similarities and differences. • Linnaeus developed binomial nomenclature, a two-word naming system. • The first word is the genus. The genus is always capitalized. • The second word is the species. The species is written in lowercase.

  6. Both the genus and the species are italicized. For example Homo sapiens (human) Felix domestica (house cat) Panthera leo (lion) Ajuga reptans (ajuga)

  7. A taxon is a group or level of organization. Linnaeus used seven taxons: Kingdom Phylum Class Order Family Genus Species Increasing similarities

  8. Problem with Linnaean System • Due to convergent evolution, organisms that are quite different from each other evolve similar body structures. • These similarities made it hard for taxonomist to classify many organisms accurately.

  9. CONVERGENT EVOLUTION The process by which unrelated organisms come to resemble each other.

  10. Scientist now understand that organisms share certain traits because of similarities in their evolutionary history. • Biologist now group organisms into categories based on evolutionary descent rather than on physical similarities.

  11. This evolutionary classification uses cladograms to show what characteristics organisms have in common. • Scientists use cladograms to understand how things are similar and different. • See page 452 and handout provided.

  12. A Cladogram

  13. Similarities in DNA and RNA • The similarities of genes in DNA and RNA are now used to help determine classification. • See handout provided.

  14. Activity: The Six-Kingdom Classification System • The current classification system now has six kingdoms and three domains. • Refer to the classification handout provided. • Record a brief description of each domain and each kingdom on the handout. • See page 458 in your textbook for descriptions.

  15. ACTIVITIES “Amino Acid Activity” “Using and Constructing a Classification Key” “How to Read a Cladogram” “Investigating Common Functions Among Diverse Organisms” “Introduction to Viruses” – How do viruses fit into the classification scheme?

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